The involvement of spirochaetes, such as the aetiologic agent of Lyme borreliosis, Barrelia burgdorferi sensu late, in Alzheimer's disease (AD), a common neuropathology, has been proposed by several groups in the past. in our laboratory, brains from 10 AD patients were analysed for the presence of B. burgdorferi sensu late by both standard and nested PCR techniques based on various target regions, such as the hbb gene (encoding the histone-like protein HBb), the fla gene (flagellin), the rrl-rrf ribosomal intergenic spacer region and the rrs gene (encoding 16S rRNA). In addition, ELISA and Western blot tests for the detection of antibodies against spirochaetal antigens were performed on 27 sera from clinical AD patients. Using these methods, we did not obtain any evidence of the involvement of B. burgdorferi in Alzheimer's disease.